1. Field of Invention
The present invention pertains to power generation systems employing gas generators that utilize natural gas as a hydrocarbon fuel source for producing combustion reactions.
2. Related Art
Cogeneration involves using a single fuel source to simultaneously produce, in the same facility, thermal energy, usually in the form of steam, and electric energy. Many cogeneration processes use an integrated, high-efficiency combined cycle to increase efficiency. Typically, a combined cycle is a steam turbine (i.e., Rankine-cycle) thermodynamically coupled with a gas turbine (i.e., Brayton-cycle). Steam and gas turbine combined cycle systems are often used where natural gas is the fuel source because natural gas tends to have a lower concentration of impurities than other fuel sources that cause corrosion, fouling and rapid deterioration in the gas turbine parts, particularly gas turbine blade surfaces.
Gas generators are attractive power generation technologies. Certain types of gas generators are capable of operating substantially free of pollutants. Exemplary high-pressure power gas generators with near-zero emission products are described in U.S. Pat. Nos. 5,709,077, 5,970,702, 5,680,764, 5,715,673, 5,956,937, 6,170,264, 6,206,684, 6,247,316, 6,389,814, 6,523,349, 6,598,398, 6,622,470 and 6,637,183, and also in U.S. Patent Application Publication Nos. 2004/0065088, 2004/0003592, 2003/0131582 and 2002/0174659. The disclosures of these patent publications are incorporated herein by reference in their entireties.
For example, in some of the power generation systems described in the previously noted patent documents, a high pressure fuel and high pressure O2 along with water are combined in a gas generator to form a combustion reaction and generate a high temperature gas. The combustion temperature is controlled by cooling water injected (e.g., via spraying) into a gas mixing chamber in the gas generator. The high pressure, high temperature steam/CO2 mixture from the gas generator is passed through a series of turbines with inter-turbine reheaters between the turbines. The gas is condensed and water is optionally recycled to the gas generator.
While power generation systems such as those described above are highly effective in producing mechanical and/or electrical energy per the requirements of a particular application, there is always the desire to maximize efficiency and reduce energy costs during system operation where possible. In particular, it would be beneficial to recover and utilize at least some of the heat losses that are typically associated with system operation of the power generation systems.